The present disclosure relates generally to antenna coils embedded in metallic structures, including security devices and, more specifically, to radio-frequency identification (RFID) and/or near field communication (NFC) locks.
Security devices, such as padlocks and other types of locks, are used to prevent access to a room, building, container, or piece of equipment. Some locks include keyed locks or combination locks. To open those locks, the user utilizes a key to open the lock or a combination of numbers, symbols, codeword, etc. to open the lock. Such devices may be used because the lock can be a constructed primarily from metallic or other durable and tamper resistant materials. Thus, it may be less likely that the lock will be damaged or broken, either due to the elements or due to attempts at breaking the lock.
RFID systems allow for convenient wireless identification and tracking of people and/or objects for various types of applications. For example, RFID systems may be used in access control applications, such as allowing users to access protected areas by holding an RFID card within proximity of a card reader coupled to a door lock. Other example applications of RFID systems include tracking products (e.g., in a retail environment), tracking people in a hospital environment, or enabling users to wirelessly process payments (e.g., using a wireless point-of-sale RFID detection system).
An RFID detection system can identify an RFID device (e.g., an RFID tag or card) when the detection system detects that the RFID device has entered the proximity of the detection system. One way to detect when an RFID device has come within proximity of the detection system is to continuously keep the detection system in an active polling mode. In the active polling mode, the detection system transmits polling signals that RFID devices within proximity of the detection system can receive. The RFID devices may then respond to the polling signals, indicating to the detection circuit that the devices are within proximity of the detection circuit and that an identification determination should be made by the detection circuit with respect to the devices.
RFID detection systems and RFID access cards have been used in buildings to substantially prevent unauthorized access to various rooms unless an authorized access card is presented to a corresponding RFID detection system. Such readers tend to include an antenna coil and a pc board that has been potted with a non-metallic, electrically nonconductive resin material inside of a non-metallic, nonconductive, plastic housing. NFC communicative devices, such as NFC capable cell phones, tend to cover the NFC antenna with a non-metallic, nonconductive cover.